Tyler asbestos workers: mortality experience in a cohort exposed to amosite.

OBJECTIVES: To examine the causes of death among 1130 former workers of a plant in Tyler, Texas dedicated to the manufacture of asbestos pipe insulation materials. This cohort is important and unusual because it used amosite as the only asbestiform mineral in the production process. High level exposure of such a specific type was documented through industrial hygiene surveys in the plant. METHODS: Deaths were ascertained through various sources including data tapes from the Texas Department of Health and the national death index files. As many death certificates as possible were secured (304/315) and cause of death assigned. After select exclusions, 222 death certificates were used in the analysis. Causes of death were compared with age, race, and sex specific mortalities for the United States population with a commercial software package (OCMAP Version 2.0). RESULTS: There was an excess of deaths from respiratory cancer including the bronchus, trachea, and lung (standardised mortality ratio (SMR) 277 with 95% confidence interval (95% CI) 193 to 385). Four pleural mesotheliomas and two peritoneal mesotheliomas were identified. The analysis also showed an increasing risk of respiratory malignancy with increased duration of exposure including a significant excess of total deaths from respiratory cancer with less than six months of work at the plant (SMR 268 with 95% CI 172 to 399). CONCLUSIONS: The importance of the cohort lies with the pure amosite exposure which took place in the plant and the extended period of latency which has followed. The death certificate analysis indicates the pathogenicity of amosite, the predominant commercial amphibole used in the United States. These data confirm a link between amosite asbestos and respiratory malignancy as well as mesothelioma.

Absence of avian pox in wild turkeys in central Mississippi.

Eastern wild turkeys (Meleagris gallopavo silvestris) (n = 1,023), obtained during winter, spring, and summer from 1983 to 1988 on Tallahala Wildlife Management Area (TWMA) (Jasper County, Mississippi, USA) were examined for avian pox lesions. Domestic turkey poults (n = 152) maintained on the area for 1 to 2 wk periods from 1987 to 1989 also were examined. Neither wild nor domestic birds showed gross evidence of pox virus infection. This study indicated that avian pox was not endemic in wild turkeys at TWMA.

Occurrence and seasonal transmission of hematozoa in wild turkeys.

The occurrence and seasonal patterns of transmission of the blood protozoa of wild turkeys (Meleagris gallopavo silvestris) were studied at Tallahala Wildlife Management Area (TWMA) (Jasper County, Mississippi, USA). Blood smears obtained from wild turkeys in winter, spring and summer, and from sentinel domestic turkeys throughout the year were examined for Haemoproteus meleagridis and Leucocytozoon smithi. Whole blood from wild turkeys captured in summer was subinoculated into malaria-free domestic turkey poults and recipient birds were examined for Plasmodium spp. The prevalence of H. meleagridis and L. smithi were not different (P greater than 0.05) between adults and juveniles or between male and female turkeys in any season. Leucocytozoon smithi was not detected in poults in summer or in juveniles examined in winter. Sentinel studies and information from wild birds revealed that transmission of H. meleagridis and L. smithi did not overlap. Haemoproteus meleagridis was transmitted from May through November, while L. smithi was transmitted only from January through April. The onset of transmission of H. meleagridis coincided with peak hatching (mid-May) and brood-rearing (May-November) of turkey poults. Plasmodium spp. were not found in turkeys from TWMA (n = 27) nor in birds from three widely separated counties (n = 28) in Mississippi.

Comparison of light and electron microscopy for defining occupational asbestos exposure in transbronchial lung biopsies.

Since asbestos burden in the lung can very among areas, the usefulness of small tissue samples for identifying past occupational exposure is examined. Simulated transbronchial biopsy samples and open lung biopsy samples were collected from autopsy material from 12 former amosite asbestos workers and ten persons from the general population. Tissue evaluation included (1) paraffin embedment and light microscopy screening for fibrosis and ferruginous bodies, and (2) tissue digestion, which was analyzed by the combination of (A) light microscopy screening for ferruginous bodies and (B) electron microscopy (EM) screening for uncoated fibers. Using standard pathology techniques to classify the small samples was generally unsuccessful, the samples being too small or their size compounding other random sampling problems. The most reliable method of establishing which transbronchial biopsy tissue samples were from the occupationally exposed group occurred when light and EM analyses were used to evaluate digested tissue. The combined data from the EM analysis of two samples per subject indicated controls had two or fewer observed asbestos fibers, while the amosite asbestos workers had six or more fibers. This distinction was valid even in those who, 21 years before sampling, had worked for only a few weeks in the asbestos plant.

Method for removing the ferruginous coating from asbestos bodies.

A new technique for removing the ferruginous coating from ferruginous bodies is described. The tissue from occupationally exposed individuals was digested in bleach and the material collected on a Nuclepore filter. The ferruginous bodies were localized by light microscopy and either cleaned on the marked filter or transferred to a marked area on a clean filter. The chemical treatment consisted of an 8% oxalic acid bath used at various temperatures. It was determined that at 75 degrees C the reaction resulted in removal of the ferruginous coat, leaving an exposed core for further analysis. This procedure overcomes the previous analytical problems of core analysis caused by the ferruginous coating.

Ferruginous body formation on a nonasbestos mineral.

Tissue from a lung biopsy specimen was submitted for electron microscopy and x-ray energy-dispersive analysis of ferruginous bodies. The presence of these entities had been used as a factor in concluding an asbestos-related tissue response. A 62-year-old man had worked for over 25 years in an iron reclamation and manufacturing facility that had no known sources of asbestos in the work environment. He had no history of recurrent respiratory problems. Combined studies in tissue sections as well as on digested specimens revealed that the core of a majority of the ferruginous bodies was an iron-rich fiber. The source of the fibers was traced to a material used in packing and insulation of the metal during the tempering process. While there is a widespread regional potential for exposure in both environmental and occupational settings, the question as to whether the dust is actually a health hazard or more of a nuisance pollutant remains unanswered. It is evident, however, that the fibrous mineral should be recognized as a stimulus for ferruginous body formation in humans.

A comparison of the ferruginous body and uncoated fiber content in the lungs of former asbestos workers.

Tissue samples from 12 former asbestos workers were digested and analyzed for ferruginous body and uncoated fiber populations. It was noted that there were large numbers of nonasbestos fibers in each of the samples. In some samples, these fibers constituted over 80% of the total uncoated fibers, and they could greatly influence the data as to asbestos content of the tissue unless differentiated by light and electron microscopic techniques, such as X-ray energy-dispersive analysis. There were great variations in the numbers of uncoated fibers per ferruginous body between the individual workers. The digested samples from lungs of 2 workers yielded no ferruginous bodies by light microscopy, even though these samples by electron microscopy contained respective loads of 780,000 and 1.2 million uncoated amphibole fibers per gram. Light microscopy examination of adjacent tissues confirmed mild fibrosis in both workers. Ferruginous bodies serve as a general marker for asbestos exposure. However, our data suggest that their absence in tissue with interstitial fibrosis from a worker with previous occupational exposure may not be sufficiently conclusive to rule out asbestos-induced disease. Rather, as shown by our data, individual exceptions may require correlated analysis by analytical electron microscopy in order to define particulate load and support the diagnosis of the disease.

The influence of amosite asbestos exposure on lung permeability.

The effect of amosite asbestos on permeability of the blood/air barrier in the lung was studied using an acute animal model. The ultrastructural tracer selected for the study was horseradish peroxidase which was given intravenously in animals that had been exposed intratracheally to asbestos. The acute period of study was either 1/2, 1, 2, 3, or 4 hr, or 1-7 or 14 days postexposure. The barrier in the normal lung was at the level of the alveolar epithelial lining. Leakage of exudate and tracer occurred through the altered barriers following asbestos exposure and the extent of leakage related directly to the degree of alveolitis and the asbestos present in the area. A trend toward recovery of the barrier occurred with the reestablishment of a more normal-appearing epithelial lining during the second week postexposure.

Asbestos content in lungs of occupationally and nonoccupationally exposed individuals.

Previous reports have indicated that a majority of the population has asbestos bodies within their lungs. These studies generally have been carried out using cohorts from urban environments. The present study compares the asbestos body levels from three unique cohorts: (1) a nonoccupationally exposed group from a large urban environment having a relatively low asbestos content, (2) patients with lung cancer from a nonurban setting, and (3) amosite asbestos workers, who worked and lived in a rural setting. The number of asbestos bodies in both the urban nonoccupationally exposed group and the patients with lung cancer was generally found to be low or below limits of detectability, with the exceptions being those persons in whom an occupational exposure was eventually found. The ferruginous body content of the occupationally exposed group varied considerably between individuals as well as between sites within the same individual.

Short-course chemotherapy for pulmonary disease caused by Mycobacterium kansasii.

Forty patients with pulmonary disease caused by Mycobacterium kansasii were treated initially with rifampin, isoniazid, and ethambutol daily for 12 months, and with streptomycin twice weekly for the first 3 months. Postchemotherapy follow-up examinations have ranged from 6 to 68 months, with an average of 31 months. One of the 40 patients (2.5%) relapsed 6 months after completion of chemotherapy. In vitro susceptibility of the mycobacteria to the drugs used, extent of disease, and/or the coexistence of other diseases did not seem to influence the outcome. This 12-month chemotherapy regimen is considered to be sufficient for the initial treatment of pulmonary disease caused by M. kansasii.

Development of monoclonal antibodies to proteins separated by two-dimensional gel electrophoresis.

We have developed techniques for the production of monoclonal antibodies using Coomassie blue-stained protein spots cut from high resolution 2-dimensional polyacrylamide gels. The gel spots were homogenized with Freund's adjuvant and injected sub-cutaneously into a mouse, at several places along the flank. After boosting twice the spleen cells were hybridized by standard methods. Hybrids, clones and ascitic fluids were also screened with antigen prepared from 2-dimensional gel spots. The spots were cut from gels, homogenized in the presence of guanidinium chloride, and extracted by shaking overnight. The acrylamide was removed, the sample dialyzed to remove denaturant and the protein labeled with 125I. An alternative method for the production of screening antigen using column chromatography is described. These techniques allow the production of monoclonal antibodies to specific protein components of complex mixtures, even in the presence of other immunodominant proteins.

Asbestos bodies and particulate matter in sputum from former asbestos workers. An ultrastructural study.

From sputum samples collected from nine former asbestos workers, one portion not needed for cytopathologic screening was fixed, embedded and sectioned for transmission electron microscopy (TEM) while a second portion was digested and collected on a Nuclepore filter for scanning electron microscopy (SEM). Energy-dispersion analysis was used in assessing inorganic matter in both preparations. The ultrastructural relationships between the ferruginous bodies and related macrophages as well as the presence of other particulate matter in the preparations were studied. Our results are the first to confirm the presence of uncoated asbestos fibers, diatomaceous earth and aluminosilicates in sputum. Our data indicate that it would be reasonable to use this analytical technique as an initial test before using invasive procedures in the diagnosis of many pneumoconioses and other lung diseases.

Acute lung response to amosite asbestos: a morphological study.

The acute morphological response to amosite asbestos in the guinea pig was studied by light microscopy and by transmission, scanning, and scanning transmission electron microscopy. Fiber identification was carried out by energy dispersive X-ray analysis. Animals were studied at postinjection intervals of 2, 4, and 12 hr and 1-7 days. Three groups of test animals were studied for each time interval. These consisted of a vascularly perfused parenchymal group and a free cell lavaged group. The information obtained was compared with saline-injected and normal control animals. The acute tissue response was characterized by intraalveolar, not interstitial, events. The early phagocytic response was shared between polymorphs and macrophages, while in the longer intervals, the macrophages were the phagocytic cell type. Packaging differences within the two types of phagocytes were seen. Endothelial stability was noted, while some edematous type I pneumocytes were observed. Fibrotic involvement was limited to some intraalveolar fibrin deposits. It is suggested that the term "free asbestos fibers" refers to an extracellular event, while intracellular fibers are coated with either a membranous sheath, a siderosome, or a classical ferruginous coating.

Method for removing the ferruginous coating from asbestos bodies.

A new technique for removing the ferruginous coating from ferruginous bodies is described. The tissue from occupationally exposed individuals was digested in bleach and the material collected on a Nucleopore filter. The ferruginous bodies were localized by light microscopy and either cleaned on the marked filter or transferred to a marked area on a clean filter. The chemical treatment consisted of an 8% oxalic acid bath used at various temperatures. It was determined that at 75 degrees C the reaction resulted in removal of the ferruginous coat, leaving an exposed core for further analysis. This procedure overcomes the previous analytical problems of core analysis caused by the ferruginous coating.

The influence of inflation levels of the lung on the morphology of the visceral pleura.

The visceral pleura was shown ultrastructurally to be a tightly adhering covering which follows closely the contour of the underlying lung parenchyma. The outer mesothelial layer was comprised of flattened cells when the lung was inflated and transformed into regions of more cuboidal cells after lung collapse. The only distinguishing factors between the visceral pleura of the younger and older animals were the increased connective tissue in the submesothelial areas of the latter and the increased numbers of vesicles found in their basal lamina. The varying degrees of lung inflation can result in marked alterations in the characteristics of the mesothelial layer of the visceral pleura.